In man, bladder outlet obstruction occurs as result of neurogenic, prostatic, and urethral stricture disease. The detrusor's initial response to chronic obstruction is the development of smooth muscle (SM) hypertrophy. Despite this increase in muscle mass, cellular force generation decreases and bladder function is impaired. The switch of detrusor smooth muscle from a differentiated, contractile phenotype to a dedifferentiated, synthetic phenotype undoubtedly plays a vital role in obstruction-induced bladder dysfunction. Although hypertrophic growth has been described in cardiac, renal, intestinal and urinary tract systems, its nature at the molecular and cellular level still remains unclear. Caldesmon is believed to be an important regulatory protein in smooth muscle contraction and bladder outlet obstruction induces alteration of caldesmon expression. Our hypothesis is that these alterations explain, at least in part, the altered contractility seen with bladder hypertrophy. Therefore, the general aim of this proposal is to study the expression and regulation of the caldesmon gene in the obstructed bladder using the rabbit partial bladder outlet obstruction model utilizing the following methods: nuclear run-off assay, cDNA cloning, nucleic acid sequencing, northern analysis, westernblot analysis, antibody generation and immunohistochemistry. The following specific aims are proposed: (1) to clone rabbit h-caldesmon cDNA, 12) to determine whether obstruction- induced detrusor smooth muscle hypertrophy alters caldesmon gene expression, (3) to develop and characterize guinea pig polyclonal antibodies that specifically recognize rabbit h- and l-caldesmon, and (4) to determine the cellular localization of caldesmon expression.